Anode mounting for electrolytic cell

ABSTRACT

IN A DIAPHRAGM-TYPE ELECTROLYTIC CELL FOR THE PRODUCTION OF CHLORINE AND CAUSTIC ALKALI FROM ALKALI METAL CHLORINE SOLUTIONS WHEREIN THE CELL HAS METAL ANODES, A CONDUCTING AND SUPPORTING CELL BASE WHICH IS COVERED WITH AN ELECTRICALLY NON-CONDUCTIVE SHEET, A TWO-POINT SEALING SYSTEM IS PROVIDED FOR BOLTING THE ANODE TO THE CELL BASE AND SEALING THE ELECTROLYTE OUT OF THE HOLE THROUGH WHICH THE BOLT PASSES.

Aug. 14, 1973 P- E. ARMSTRONG ET AL ANODE MOUNTING FOR ELECTROLY'IHJCELL Filed Jan. 31, 1972 United States Patent O 3,752,756 ANODE MOUNTINGFOR ELECTROLYTIC CELL Phillip E. Armstrong, Baton Rouge, La., Webster L.Kaiser, Jr., Cleveland, Tenn., and Newlin S. Nichols, Dearhorn, John E.Schmidt, Southgate, and Orlando W. Stephenson III, Ann Arbor, Mich,assignors to BASF Wyandotte Corporation, Wyandotte, Mich,

Filed Jan. 31, 1972, Ser. No. 222,108 Int. Cl. B01k 3/10 US. Cl. 204-2526 Claims ABSTRACT OF THE DISCLOSURE In a diaphragm-type electrolyticcell for the production of chlorine and caustic alkali from alkali metalchlorine solutions wherein the cell has metal anodes, a conducting andsupporting cell base which is covered with an electricallynon-conductive sheet, a two-point sealing system is provided for boltingthe anode to the cell base and sealing the electrolyte out of the holethrough which the bolt passes.

BACKGROUND (1 Field of the invention This invention relates to a newmeans for mounting metal anodes in an electrolytic cell which has aconducting and supporting cell base.

(2) Description of the prior art US. Pat. 3,591,483 granted July 6, 1971on an applin cation filed by R. E. Loftfield et al. discloses adiaphragmtype electrolytic cell which is especially suited to the use ofdimensionally stable (metal) anodes. The cell is chararacterized ashaving a metal base which serves as a rigid support for the anodes, as aconductor for distributing electrical current to the anodes and as arigid support for the cell can. Furthermore, a sheet of electricallynon-conductive material covers the entire cell base and serves toinsulate the contact between the cell can and the cell base and alsoprovides a hydraulic seal to prevent leakage of the electrolyte. Thissystem is satisfactory as long as the non-conductive cover maintains itsphysical characteristic but these covers being organic materials aresusceptible to deterioration due to the extremely adverse environmentalconditions, e.g. heat and corrosiveness of electrolyte. Thisdeterioration causes a reduction in the pressure on the electricalconnection resulting in power insufliciencies plus allowing theelectrolyte to seep into the electrical connection. Therefore, it isdesirable to provide an improved means of mounting metal anodes in anelectrolytic cell.

SUMMARY OF THE INVENTION In accordance with this invention there isprovided in a diaphragm-type electrolytic cell for the production ofchlorine and caustic alkali from alkali metal chloride solutions whereinthe cell has metal anodes, a conducting and supporting cell base meanshaving holes disposed therein for receipt of anode support studs and anelectrically nonconductive sheet covering the entire cell base andhaving holes therein in axial alignment with the holes in the cell base,the improvement comprising in combination (1) at the base of the metalanode and surrounding said anode support stud an O-ring which isretained in position by a retaining flange attached to or adjoining thebase of the anode, the flange completely encircling the O-ring, theflange having a height slightly less than the diameter of of the O-ringwhereby the O-ring is placed under compression when the stud is inelectrical connection with the cell base and (2) the anode support studhaving a pressure receiving shoulder which corresponds with and mates 3,752,756 Patented Aug. 14, 1973 with a similar pressure receivingshoulder in the cell base, the O-ring and the pressure receivingshoulder being so positioned that when the anode supporting stud isconnected to the cell base that both the O-ring and the pressurereceiving shoulder are placed under compression at substantially thesame time yet the compression placed on one is independent of thecompression placed on the other whereby the compression of the pressurereceiving shoulder of the anode support stud is maintained independentof the changes of compression in the O-ring due to the changing physicalproperties of the O-ring and the electrically non-conductive sheet.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a cross-sectional endView of an anode installed in an electrolytic cell with the improvedmounting system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the invention as shown in thedrawings there is provided a cell bottom metal base 20 which acts asboth a strength member and a bus bar member and is covered with anelectrically non-conductive sheet 18. To the bottom of the anode 10 isattached anode stud (or bolt) 16 which has metal-to-metal contactshoulder 26, 26a which has the same configuration as metal-to-metalcontactshoulder 24, 24a of metal base 20. These contact shoulders can beeither square or conical. O-ring 14, 14a is slipped over anode stud 16and retained in place by retaining ring (or flange) 12, 12a which isattached to the base of metal anode 10. Retaining ring 12 is concentricwith and completely surrounds O-ring 14 except that retaining ring 12has a height slightly less than the diameter of O-ring 14. Preferablythis height will be about from 0.5 to 0.9 of the diameter of O-ring 14and corresponds to the amount of original compression of O-ring 14planned for. The metal-to-metal contact shoulders 24, 26 are sopositioned that when they are melted at substantially the same timeO-ring 14 is placed under compression and flange or retaining ring 12,will contact electricallynon-conductive sheet 18. Anode stud 16 ismaintained in mechanical and electrical connection with metal base 20 byproper tightening of stud nut 22. Metal-to-metal contact shoulders 24,26 are also adequately prepared for good electrical contact efficiencyby well known techniques to those skilled in the art. When anode stud 16is properly installed and stud nut 22 correctly tightened retaining ring12 initally exerts some compression on non-conductive sheet 18. Duringcell operation electrically non-conductive sheet 18 due to thecorrosiveness of the electrolyte and temperature attained will tend todeteriorate and relax. Such relaxation is compensated for by initiallyhaving O-ring 14 under compression behind retaining ring 12.Furthermore, the mechanical and electrical connection of anode stud 16being based on metal-to-metal contact shoulders 24, 26 and stud nut 22is unaifected by such relaxation.

In the drawing retaining ring 12 has been shown as at tached to and apart of metal anode 10. However, it is within the scope of thisinvention that retaining ring 12 also be separate and independent fromanode 10. It will be seen that use of an independent retaining ring 12permits the substitution of different sizes of O-rings 14 and simplerfabrication whereas an attached retaining ring 12 permits a moreconvenient assembly of the invention.

While it is shown in the drawing to use a flat nut 22, it is also wellknown in the art to use in combination with nut 22 a flat washer, or abeveled washer in connection with a chamfered opening or using a bevelednut with the chamfered opening in the metal base 20. The exactarrangement of how to obtain a good mechanical and electricallyconductive connection with the metal base 20 is well known to thoseskilled in the art and further elaboration need not be made at thispoint.

The O-ring 14 and electrically non-conductive sheet 18 can be of any ofthe well known materials of the prior art including but not limited to,as applicable using ordinary engineering skills, rubber, chlorinatedplastics, and polymers and copolymers of trifluorochloroethylene,tetrachloroethylene and tetrafluoroethylene sold under trade names suchas Teflon and Kel-F. It is readily apparent that in some instances theO-ring 14 and non-conductive sheet 18 will be made out of dilferentmaterials. However, materials such as the tetrafluoroethylene polymercan be utilized in both applications. In addition, materials such asasphaltic mastics can be used for the electrically non-conductive sheet18. As has been pointed out the anode stud 16 holes or apertures in theelectrically non-conductive sheet 18 and metal base 20 are in axialalignment so that anode stud 16 plane is perpendicular to the plane ofthe metal base 20. Furthermore, as pointed out in discussing the studnut 22 the edge of the aperture not covered by the electricallynon-conductive sheet 18 may be chamfered to receive a beveled nut orwasher in place of flat stud nut 22 shown in the drawing.

The actual configuration of metal anode being beyond the scope of thisinvention is a matter of ordinary engineering skills. Suffice it to saythat anode 10 can be either a sheet or plate metal anode or an expandedmesh anode. As is well known in the art, metal anode 10 can be coatedwith a platinum metal or metal oxide coating or mixture of metal andoxide to increase the efliciency of the anode.

The anode 10 and anode stud 16 are suitably made from titanium, arestrictive valve metal or an alloy thereof. By restrictive valve metalsit is meant that the metals of titanium, tantalum and niobium.Preferably titanium is employed and it is normally a commercially puregrade such as electrolytic grade. Alloys of titanium may be employed aslong as the alloy meets the criterion of passivity, metal alloys whichbecome passivated when polarized anodically can remain passive wellbeyond the anodic potential needed to convert a chloride ion tochlorine. The phenomenon of passivity in this connection is discussed inan article by Greene appearing in the April 1962 issue of Corrosion,pages l36-t to 142-t wherein reference may be made to Figure 1 of thearticle which de scribes typical active-passive transition of a metaltowards a corrosive medium. Titanium alloys of aluminum, vanadium,palladium, chromium or tin can be employed in which the latter metalsare present as less than 10 percent of the alloy. In addition anode stud16 may be made of copper and clad with one of the previously enumeratedmetals or alloys. Furthermore, it is well known that the electricalefliciency of the connection of anode stud 16 can be improved byplatinizing the threads of the stud which engage stud nut 22.

Metal anode 10 and anode stud 16 of this invention have been describedin terms of fabrication from titanium metal since in terms ofavailability and cost it is the metal of choice.

The number of anode studs 16 employed with each metal anode 10 is amatter of engineering choice and will be influenced by the size andconfiguration of the anode as well as electrical supply requirements.Satisfactory results are obtained by the use of 2, 3 or more anodestuds.

Since the metal base is protected from the corrosive nature of the cellelectrolyte the base can be made from any electricity carrying metal ofchoice such as steel, copper or aluminum. Additionally metal base 20 canbe a composite of a strength member and a bus bar member, e.g. a steelload bearing sheet over a copper bar.

Many other modifications and ramifications of this invention willnaturally suggest hemselves to those skilled in the art based on thisdisclosure. These ramifications and modifications are intended to becomprehended as within the scope of this invention.

Having thus described the invention, what it is desired to claim andsecure by Letters Patent is:

1. In a diaphragm-type electrolytic cell for the production of chlorineand caustic alkali from alkali metal chloride solutions wherein saidcell has metal anodes, a conducting and supporting cell base meanshaving holes disposed therein for the receipt of anode support studs andan electrically non-conductive sheet covering the entire cell base andhaving holes therein in axial alignment with said holes in the cellbase, the improvement comprising in combination (1) at the base of themetal anode and surrounding said anode support stud an O-ring which isretained in position by a retaining flange adjacent the base of saidanode, said flange completely encircling said O-ring, said flange havinga height less than the diameter of said O-ring whereby said O-ring isplaced under compression when said stud is in electrical connection withsaid cell base and (2 said anode support stud having a pressurereceiving shoulder which corresponds with and mates with a similarpressure receiving shoulder in said cell base, said O-ring and saidpressure receiving shoulder being so positioned that when said anodesupport stud is connected to said cell base that both said O-ring andsaid pressure receiving shoulder are placed under compression atsubstantially the same time yet the compression placed on one isindependent of the compression placed on the other whereby thecompression of the pressure receiving shoulder of said anode supportstud is maintained independently of the changes of compression in theO-ring due to changing physical properties of said O-ring and saidelectrically non-conductive sheet.

2. The anode support stud of claim 1 wherein the pressure receivingshoulder is square.

3. The anode support stud of claim 1 wherein the pressure receivingshoulder is conical.

4. The retaining flange of claim 1 wherein the flange height is 0.5 to0.9 of the diameter of said O-ring.

5. The retaining flange of claim 1 wherein the flange is attached to theanode.

6. The retaining flange of claim 1 wherein the flange is a separatering.

References Cited UNITED STATES PATENTS 9/1918 Wheeler 204-286 2/1969McWhorter 204286 US. Cl. X.R.

